Accident Summary
On September 7, 2025, at about 0932 eastern daylight time, a CubCrafters Carbon Cub EX airplane, registration N40DT, sustained substantial damage during an accident near Thompsonville, Michigan. The private pilot was not injured; the passenger sustained minor injuries. The airplane was operating under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Flight and Power Loss
The airplane departed from Thompsonville Airport (7Y2) around 0917. Shortly after takeoff on a local flight, the pilot noticed a flicker on the Garmin G3X Touch display but no low voltage warning. Checking the engine monitoring display, he observed that the alternator was not charging and the system showed 12.8 volts direct current (VDC). The pilot immediately initiated a climbing turn back to 7Y2. At approximately 4,000 ft, he attempted several methods to restore alternator function, including cycling both the field and main alternator circuit breakers multiple times. He then checked the voltage of the backup ignition battery, which read 12.8 VDC.
Deciding to conserve the backup battery, the pilot continued operating on the main battery until a low voltage warning appeared. While on final approach to 7Y2, the low voltage warning activated on the Garmin G3X Touch display. The pilot switched to the backup ignition battery; however, the voltage dropped from 12.8 VDC to 0 VDC, and the engine experienced a total loss of power. The backup battery proved faulty, providing power for only one to two minutes.
Forced Landing and Damage
On short final, at about 300 ft altitude, the pilot performed a forced landing near trees. During the landing, the airplane came to rest nose down in the trees. The accident resulted in substantial damage to both wings and the wing struts.
Postaccident Examination
The wreckage was recovered to Thompsonville Airport (7Y2). Postaccident examination of the engine revealed a broken ring terminal on the Denso 021080-0760 12-volt alternator. The pilot reported that the broken ring terminal originated from a factory-built harness.
The pilot had built the experimental airplane from a kit in 2025. The aircraft was powered by a CubCrafters CC363i (Lycoming Engines YIO-360-EXP128) reciprocating engine and equipped with a two-blade carbon fiber composite Hartzell Propeller HC-C2YR-IN/NG8301 Trailblazer Homebuilt constant speed propeller.